To elucidate the roles of the cerebellum, particularly the flocculus and vermal lobus VI and VII, in the control of eye position and smooth pursuit eye movements, single unit recording will be made from Purkinje cells (output neurons) and mossy and climbing fibers (input neurons) from monkeys trained to fixate a visual target and to track the target when it moves. The research during the coming year will be focused on the study of interactions between the oculomotor signals coming from brain stem oculomotor centers to the flocculus and the visual inputs. Experiments will be designed to study particularly the following points: (1) Receptive field properties of the Purkinje cells which are driven by visual stimulus movements at the velocity of smooth pursuit eye movements. (2) Response properties of visual mossy fibers and compare these with the behavior of brain stem visual neurons which may give rise to mossy fiber projections to the flocculus. (3) Effects of visual input signals on discharges of Purkinje cells during retinal image motions induced either by movements of the visual environment or by eye movements.